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• Add frame to video in specified position

  28 septembre 2015, par QUANGPHAT ĐINH

  I’m using Aforge libs to read and write video files (the libs is here : http://www.aforgenet.com/framework/features/ffmpeg.html).

  Now I want to export a specific frame to edit, then import it back to the video.

  I could export frame by frame but I don’t know how to add it back to the video in specific frame. what should i do now ?

• How to convert char buffer (with pcm audio data) to short buffer

  18 décembre 2012, par testCoder

  I have char pAudioBuffer buffer which i got from function ffmpeg :

  int len = avcodec_decode_audio3(av_codec_context,
  
              (int16_t *) pAudioBuffer, &out_size, &packet);

  I know that audio format is two bytes per sample, i need to convert every two bytes to short value, i have tried to use code snippet below, but i often got zero instead of short value :

  int shortBufIndex = 0;
  
  for (int i = 0; i < (out_size); i += 2) {
  
      char b1 = pAudioBuffer[i];
  
      char b2 = pAudioBuffer[i + 1];
  
      short sample = atoi(&b1) + atoi(&b2);
  
      shortBuffer[shortBufIndex] = sample;
  
      shortBufIndex++;
  
      LOGI("BUFFER_ITEM='%d'", sample);
  
  }

  What i'm doing wrong, how to convert every two bytes in char buffer to short and and back.

  UPDATE :

  system's byte order is LITTLE_ENDIAN i have test it like this : Endianness of Android NDK

  How can i convert every two bytes in buffer to sample of short type and back. Please can you provide any code sample.

  UPDATE

  I have tried to access to short as pairs, here is my fixed code, but it not work, i don't hear any sound :

      int shortBufIndex = 0;
  
      for (int i = 0; i < (out_size); i += 2) {
  
          char * byte = (char *) pAudioBuffer[i];
  
          short * sample = byte;
  
          shortBuffer[shortBufIndex] = sample;
  
  }

  What i'm doing wrong ?
  I need conversion like this : byte array to short array and back again in java but in c.

• Merge videos with different start times and show them on a grid

  1er août 2017, par shamaleyte

  I have multiple video files of a conference call. However, each participant joined the call at a different time, which resulted in the fact that each video file has a different start time offset values.

  Video   Start Time
  
  ------------------
  
  Video1  00:00
  
  Video2  00:10
  
  Video3  01:40

  My purpose is to play back this conference. However, I did not record the conference as 1 video, it is recorded with multiple video files, instead.
  How do I stitch these videos ?

  There is also a paid solution to merge video fragments to a single clip – this will make the client-side much simpler. But can I do it for free ?

  The expected outcome is to have one video showing three videos on a grid.
  When ffmpeg stitches the videos, it should consider their start time values properly so that the videos are played accordingly.